if your worryed about being tracked. use the new nodezilla grid p2p, its compleatly anonymous. the reason with classic p2p software, such as limewire, that you can be tracked is it is based on making a direct tcp connection between sharer and downloader. therefore both must know each others ip address.
nodezilla is radically different, each peer is connected to a few nearby peers, who are in turn connected peers near them, ect.. When you start downloading a file you never make a direct connection to the sharer. the data is send through the grid via multiple peers hopping from peer to peer along on the way. finding the shortest path back to you.
sharer->node1->node2->node3->you.
effectivly everyone is acting as a proxy for everyone else. no one can tell whos shareing, downloading or just routing the data. also the data is cashed along the way so if the sharer is gone the data is still avalable. its based on the freenets topology, with a lot of improvements. theres been a few other atempts at this before such as ants or mute p2p but none have come close to what nodezilla has achived. so in other words you CAN do the crime and never worry about doing the time!!